DESCRIPTION: (Adapted from the candidate's description) The goals of this translational research project are to genetically and clinically dissert the imprinted genes underlying each component of Prader-Willi syndrome (especially the gene causing obesity), and to explore the potential role of early childhood morbid obesity plays in mental retardation. This will be accomplished by screening for mutations in candidate genes for various phenotypic components of PWS; performing psychometric testing on children with early onset morbid obesity and their families; and correlating hormonal and neurotransmitter levels from blood and CSF with the psychometric and mutation analyses.